# Esperanto prefixes: all 10 official with examples

Source: https://esperantopedia.org/grammar/prefixes/
Language: en
Updated: 2026-10-28

> Esperanto has 10 official prefixes: bo-, ĉef-, dis-, ek-, eks-, ge-, mal-, mis-, pra-, re-. Meanings, examples and a close look at mal-.

Esperanto has **10 official prefixes**: *bo-, ĉef-, dis-, ek-, eks-, ge-, mal-, mis-, pra-* and *re-*. Nine come from the *Fundamento de Esperanto* (1905); *mis-* became official in 1929. A prefix adds a fixed meaning and never changes the word class: *fermi* "to close" → *malfermi* "to open".

Prefixes are one part of Esperanto [word building](https://esperantopedia.org/grammar/word-building/). The other part, the 31 [suffixes](https://esperantopedia.org/grammar/suffixes/), goes after the root.

## The 10 official prefixes

| Prefix | Meaning | Examples | Translation |
|---|---|---|---|
| *bo-* | related by marriage, in-law | *bopatro, bofrato, bofilino* | "father-in-law, brother-in-law, daughter-in-law" |
| *ĉef-* | chief, main | *ĉefurbo, ĉefministro* | "capital city, prime minister" |
| *dis-* | apart, in all directions | *disĵeti, disdoni* | "to scatter, to hand out" |
| *ek-* | sudden or starting action | *ekdormi, ekridi, ekvidi* | "to fall asleep, to burst out laughing, to catch sight of" |
| *eks-* | former, ex- | *eksedzo, eksreĝo* | "ex-husband, former king" |
| *ge-* | both sexes together | *gepatroj, gefratoj, geedzoj* | "parents, siblings, married couple" |
| *mal-* | exact opposite | *malbona, malgranda, malfermi* | "bad, small, to open" |
| *mis-* | wrongly | *miskompreni, misuzi, miskalkuli* | "to misunderstand, to misuse, to miscalculate" |
| *pra-* | primeval; one generation further | *praavo, praarbaro* | "great-grandfather, primeval forest" |
| *re-* | again; back | *relegi, reveni, redoni* | "to reread, to come back, to give back" |

Sources count slightly differently. PMEG and lernu list the ten above. The English Wikipedia lists *fi-* instead of *ĉef-*, and the ReVo editors' affix overview reaches 12 by adding both *fi-* and the preposition *trans-*. PMEG treats *fi* as an official interjection that is also used like a prefix (*fihomo* "a vile person"), and *trans-* as a preposition. This page follows PMEG: ten.

malbona = bad | bon = good | ferm = close | leg = read
ekdormi = to fall asleep | dorm = sleep
bopatrino = mother-in-law | patr = father

## Mal-: the opposite

*Mal-* gives the **exact opposite** of a word (PMEG). One root plus *mal-* covers both ends of a scale, so you learn one root instead of two. It works on every kind of word:

| Word class | Base word | With *mal-* |
|---|---|---|
| Adjective | *bona* "good", *granda* "big", *varma* "warm" | *malbona* "bad", *malgranda* "small", *malvarma* "cold" |
| Verb | *fermi* "to close", *helpi* "to help", *ami* "to love" | *malfermi* "to open", *malhelpi* "to hinder", *malami* "to hate" |
| Noun | *amiko* "friend", *lumo* "light", *ordo* "order" | *malamiko* "enemy", *mallumo* "darkness", *malordo* "disorder" |
| Adverb, particle | *pli* "more", *plej* "most", *supre* "above" | *malpli* "less", *malplej* "least", *malsupre* "below" |
| Preposition | *antaŭ* "in front of" | *malantaŭ* "behind" |

On its own, *mal-* is also a root: *malo* "the opposite", *male* "on the contrary".

### Mal- versus ne-

*Ne* means simply "not"; *mal-* means the opposite. *Malagrabla* is "unpleasant", while *neagrabla* is "not pleasant" – neither nice nor nasty. PMEG gives *mallaŭdi* "to criticise" against *ne laŭdi* "not to praise".

### Where mal- does not work

*Mal-* is used only where a real opposite exists. Many pairs have two separate roots: *tago – nokto* "day – night", *komenci – fini* "begin – end", *nigra – blanka* "black – white" (PMEG). Some speakers use separate roots like *kurta* for *mallonga* "short", but these remain far less common than the *mal-* forms. A good [dictionary](https://esperantopedia.org/dictionary/) shows which pairs exist.

## Notes on the other prefixes

- **ek-** goes on [verbs](https://esperantopedia.org/grammar/verbs/) and has two senses: the start of an action (*ekdormi* "to fall asleep") and a sudden, short action (*ekkrii* "to cry out"). On its own: *eki* "to begin".
- **re-** means "again" (*relegi* "to reread") or "back" (*reveni* "to return"). On its own: *ree* "again".
- **ge-** is normally plural: *gepatroj* "parents", *geedzoj* "husband and wife". The singular *gepatro* "parent" is a newer, experimental use (PMEG).
- **bo-** never stands alone: *bopatrino* "mother-in-law", *bofilo* "son-in-law".
- **pra-** goes back in time: *praavo* "great-grandfather", *prapraavo* "great-great-grandfather", *praulo* "ancestor".
- **eks-** marks a former role: *eksedzino* "ex-wife". On its own: *eksa* "former", *eksiĝi* "to resign".
- **mis-** adds the idea of error without reversing the meaning: *misdirekti* "to misdirect". Compare *mal-*, which flips the meaning.
- **ĉef-** is also an ordinary root: *ĉefo* "boss", *ĉefa* "main".
- **dis-** spreads things apart: *disiĝi* "to separate, to disperse".

## Prepositions and other words used as prefixes

Many official words work like prefixes without being counted as such. [Prepositions](https://esperantopedia.org/grammar/prepositions/) are the largest group: *alveni* "to arrive", *eliri* "to go out", *kunlabori* "to cooperate", *senhejma* "homeless". Others include *ne-* (*nekredebla* "unbelievable"), *for-* (*foriri* "to go away"), *mem-* (*memstara* "independent") and the root *vic-* (*vicprezidanto* "vice-president").

## Unofficial prefixes

These prefixes are **not official affixes**. They come neither from the *Fundamento* nor from an Academy decision, so you can speak the language well without them. Words built with them are still common in science, technology and everyday speech, and many appear in dictionaries such as ReVo and the PIV. PMEG describes 29 of them and covers the 24 SI unit prefixes separately.

Most are international prefixes. They are fine inside words that already exist in other languages, such as *ultrasono* "ultrasound". PMEG advises against coining new words with them when an Esperanto element does the same job: *kontraŭ-*, *super-*, *sub-*, *antaŭ-* or *ĉef-*. It also notes that six of them are missing from the PIV dictionary: *afro-, aŭdio-, aŭto-, eŭro-, stif-, video-*.

| Prefix | Meaning | Example | Note |
|---|---|---|---|
| *afro-* | African | *afroamerikano* "African American" | Scarcely used. |
| *anti-* | opposed to, hostile | *antifaŝisto* "anti-fascist", *antimaterio* "antimatter" | *Kontraŭ-* is usually better, but technical terms like *antimaterio* are accepted. |
| *arĥi-, arki-* | chief, highest | *arĥiduko* "archduke" | Use it only where an international word with *arĥi-* exists. Otherwise use *ĉef-*. "Archbishop" is *ĉefepiskopo*: ReVo marks *arĥiepiskopo* as better avoided. |
| *aŭdio-* | audio technology | *aŭdiodisko* "audio disc" | PMEG prefers the root *aŭdi-*. |
| *aŭto-* | self, own | *aŭtodidakto* "self-taught person" | Avoid it for "automatic": it clashes with *aŭto* "car". Say *aŭtomata*. |
| *bio-* | life, living thing | *biografio* "biography", *biodiverseco* "biodiversity" | Increasingly felt as a real prefix. Many *bio-* words are also single roots. |
| *des-* | removal, undoing | *desinfekti* "to disinfect", *desherbi* "to weed" | Proposed but little used. PMEG prefers *mal-* or *sen-…-ig-*. Not the particle *des* in *ju pli … des pli …* "the more … the more …". |
| *eko-* | ecological | *ekosistemo* "ecosystem", *ekoturismo* "ecotourism" | In use. It is a short form of *ekologia*. |
| *eŭro-* | European | *Eŭrovizio* "Eurovision" | Discouraged: it clashes with *eŭro* "euro". Use *Eŭrop-*. |
| *hiper-* | excessive, over | *hiperacideco* "hyperacidity" | Science. *Super-* or *tro* is usually clearer. |
| *infra-* | below | *infrasono* "infrasound" | Normally *sub-*. Say *transruĝa*, not *infraruĝa*, for "infrared". |
| *ko-* | complement (mathematics) | *kosinuso* "cosine" | A true prefix only in mathematics. *Kooperativo* "cooperative" and similar words are single roots. |
| *kver-* | transverse | *kversekco* "cross-section" | Technical. The usual word is *transversa*. |
| *makro-* | large-scale, huge | *makromolekulo* "macromolecule" | Science. Compare *mikro-*. |
| *meta-* | about itself, one level up | *metalingvo* "metalanguage", *metapoezio* "poetry about poetry" | Science and art. *Metafiziko* "metaphysics" is a separate word, not "physics about physics". |
| *mikro-* | very small | *mikrofilmo* "microfilm", *mikroorganismo* "microorganism" | Also an SI prefix (see the table below). |
| *mini-* | very small, very short | *minijupo* "miniskirt", *minigolfo* "mini golf" | Used when an international word exists. The Esperanto way is *-et-*. |
| *mono-* | one, single | *monorelo* "monorail" | Clashes with *mono* "money". PMEG prefers *unu-*: *unurelo*. |
| *pre-* | before | *prefaco* "preface", *prelego* "lecture" | Those are established single roots. For new words use *antaŭ-*. |
| *proto-* | first, original | *prototipo* "prototype" | Science and technology. |
| *pseŭdo-* | false, fake | *pseŭdonimo* "pseudonym" | Zamenhof often used it as a real prefix. PMEG prefers *ŝajn-*, *kvazaŭ-* or *kaŝ-*. |
| *retro-* | backwards | *retroiri* "to go backwards", *retroaktiva* "retroactive" | Fairly common. It is clearer than *re-*, which has two senses. |
| *san-* | saint | *Sanfrancisko* "San Francisco" | Place names only. PMEG advises *Sankta* or the original form, not mixtures like *Sandomingo*. |
| *semi-, hemi-* | half | *semicirklo* "semicircle", *hemisfero* "hemisphere" | Fairly common where an international word exists. PMEG prefers *duon-*. |
| *stif-* | step-relative (kinship) | – | Proposed in place of *duon-* or *vic-* in some kinship words. Scarcely used. |
| *tele-* | far, at a distance | *televidi* "to watch television", *telekomuniki* "to communicate at a distance" | PMEG: very needed in the modern world, so use it freely. |
| *termo-* | heat | *termometro* "thermometer", *termostato* "thermostat" | For new words PMEG advises *varm-*, to avoid a clash with *termo* "term". |
| *ultra-* | extreme, beyond | *ultrasono* "ultrasound", *ultraviola* "ultraviolet" | Technical. For new words PMEG advises *trans-* or *ekstrem-*. |
| *video-* | video technology | *videofilmo* "video film" | PMEG prefers the root *vide-*. |

### SI unit prefixes

PMEG lists 24 prefixes for units of measurement. They follow the international SI system and go only before unit names: *kilo-* + *metro* → *kilometro* "kilometre". Several of the resulting words are already official roots, and PMEG advises against making Esperanto-only words with these prefixes.

| Prefix | Factor | English name | Example |
|---|---|---|---|
| *kveta-* | 10³⁰ | quetta- | *kvetagramo* "quettagram" |
| *rona-* | 10²⁷ | ronna- | *ronagramo* "ronnagram" |
| *jota-* | 10²⁴ | yotta- | *jotagramo* "yottagram" |
| *zeta-* | 10²¹ | zetta- | *zetagramo* "zettagram" |
| *eksa-* | 10¹⁸ | exa- | *eksagramo* "exagram" |
| *peta-* | 10¹⁵ | peta- | *petagramo* "petagram" |
| *tera-* | 10¹² | tera- | *teragramo* "teragram" |
| *giga-* | 10⁹ | giga- | *gigaherco* "gigahertz" |
| *mega-* | 10⁶ | mega- | *megavato* "megawatt" |
| *kilo-* | 10³ | kilo- | *kilogramo* "kilogram" |
| *hekto-* | 10² | hecto- | *hektolitro* "hectolitre" |
| *deka-* | 10¹ | deca- | *dekametro* "decametre" |
| *deci-* | 10⁻¹ | deci- | *decilitro* "decilitre" |
| *centi-* | 10⁻² | centi- | *centimetro* "centimetre" |
| *mili-* | 10⁻³ | milli- | *milimetro* "millimetre" |
| *mikro-* | 10⁻⁶ | micro- | *mikrometro* "micrometre" |
| *nano-* | 10⁻⁹ | nano- | *nanosekundo* "nanosecond" |
| *piko-* | 10⁻¹² | pico- | *pikosekundo* "picosecond" |
| *femto-* | 10⁻¹⁵ | femto- | *femtosekundo* "femtosecond" |
| *ato-* | 10⁻¹⁸ | atto- | *atosekundo* "attosecond" |
| *zepto-* | 10⁻²¹ | zepto- | *zeptosekundo* "zeptosecond" |
| *jokto-* | 10⁻²⁴ | yocto- | *joktosekundo* "yoctosecond" |
| *ronto-* | 10⁻²⁷ | ronto- | *rontosekundo* "rontosecond" |
| *kvekto-* | 10⁻³⁰ | quecto- | *kvektosekundo* "quectosecond" |

The examples are regular combinations of a prefix and a unit name. PMEG names *kilo-, hekto-, deci-, centi-* and *mili-* as the most frequent. The four newest prefixes (*kveta-, rona-, ronto-, kvekto-*, added to the SI in 2022) are hardly used yet.

Two look-alikes need care. *Eksa-* (10¹⁸) is not *eks-* "former", and *mikro-* is also the general prefix for "very small" from the list above.

## Examples in sentences

- *La butiko malfermiĝas je la naŭa.* – "The shop opens at nine."
- *Bonvolu ne miskompreni min.* – "Please don't misunderstand me."
- *Miaj gepatroj loĝas en Varsovio.* – "My parents live in Warsaw."
- *Post la koncerto la homoj disiris.* – "After the concert the people went their separate ways."
- *Subite la bebo ekploris.* – "Suddenly the baby burst into tears."
- *Mi relegis la leteron antaŭ ol respondi.* – "I reread the letter before answering."
- *Mia bopatrino kuiras tre bone.* – "My mother-in-law cooks very well."
- *Ŝi estas la ĉefkuiristo de la restoracio.* – "She is the head chef of the restaurant."
- *Niaj prapatroj vivis tute alie.* – "Our ancestors lived quite differently."

## Common questions

### How many prefixes does Esperanto have?
Ten official ones: *bo-, ĉef-, dis-, ek-, eks-, ge-, mal-, mis-, pra-, re-*. Some sources list *fi-* instead of *ĉef-*, and many prepositions also work like prefixes. PMEG also describes 29 unofficial prefixes and 24 SI unit prefixes.

### What does mal- mean in Esperanto?
*Mal-* turns a word into its exact opposite: *bona* "good" → *malbona* "bad", *fermi* "to close" → *malfermi* "to open".

### What is the difference between mal- and ne-?
*Ne* just denies: *neagrabla* is "not pleasant". *Mal-* states the opposite: *malagrabla* is "unpleasant".

### Can a prefix be used as a word on its own?
Yes. Most prefixes take endings like any root: *eksa* "former", *ree* "again", *malo* "the opposite", *eki* "to begin".

### Which prefix was added after 1905?
Only *mis-*, made official in 1929. All the others come from the Fundamento.

### Are kilo-, mega- and mili- official Esperanto prefixes?
No, but they are the accepted way to name multiples of units. They go only before unit names (*kilometro* "kilometre", *megavato* "megawatt", *milimetro* "millimetre"), following the international SI system.

### Which unofficial prefixes are used most?
Among the general ones, PMEG calls *tele-* (*televidi* "to watch television") very needed. *Eko-*, *bio-*, *retro-* and *mini-* are also common. For measurements the most frequent are *kilo-, hekto-, deci-, centi-* and *mili-*.

## Sources

- [PMEG – Prefixes (list of ten)](https://bertilow.com/pmeg/vortfarado/afiksoj/prefiksoj/index.html)
- [PMEG – MAL](https://bertilow.com/pmeg/vortfarado/afiksoj/prefiksoj/mal.html)
- [PMEG – MIS (official since 1929)](https://bertilow.com/pmeg/vortfarado/afiksoj/prefiksoj/mis.html)
- [PMEG – Afiksecaj elementoj (words used like affixes)](https://bertilow.com/pmeg/vortfarado/afiksoj/afiksecaj_elementoj/index.html)
- [PMEG – Unofficial affixes](https://bertilow.com/pmeg/vortfarado/neoficialaj_afiksoj/index.html)
- [PMEG – Unofficial prefixes (list of 29)](https://bertilow.com/pmeg/vortfarado/neoficialaj_afiksoj/prefiksoj/index.html)
- [PMEG – International affixes (SI unit prefixes)](https://bertilow.com/pmeg/vortfarado/neoficialaj_afiksoj/internaciaj.html)
- [PMEG – Other affix-like words (fi)](https://bertilow.com/pmeg/vortfarado/afiksoj/afiksecaj_elementoj/aliaj_vortetoj.html)
- [ReVo team – Official and unofficial affixes](https://revuloj.github.io/temoj/afiksoj.html)
- [ReVo – kilo-](https://reta-vortaro.de/revo/art/kilo.html)
- [Akademio de Esperanto – Akademia Vortaro, explanations (MIS 1929)](https://www.akademio-de-esperanto.org/akademia_vortaro/klarigoj.html)
- [Universala Vortaro (Fundamento)](https://www.akademio-de-esperanto.org/fundamento/universala_vortaro.html)
- [lernu – Prefiksoj](https://lernu.net/gramatiko/prefiksoj)
- [Wikipedia – Esperanto vocabulary](https://en.wikipedia.org/wiki/Esperanto_vocabulary)